Hutton asserts that Lucas’ use of Gödel’s theorem against Mechanism is incorrect because of the impossibility to assume human minds’ consistency: he tries to show that there is a non-zero probability of a mind’s embracing mutually inconsistent propositions; moreover Hutton maintains that the request of human minds’ consistency is a request of infallibility. Lucas replies that the mistake of Hutton’s argument consists in his assigning probabilities to a mind’s accepting any proposition without considering what that mind has done hitherto, while human beings are guided in their accepting a proposition as true by what they have already accepted. Besides, Lucas argues that his argument doesn’t require human infallibility but only that human beings have adequate backing for what they assert and that – in this sense – consistency is not something that can be established but a necessary assumption to begin any thinking at all.
